Long term objectives of the proposed research project include the understanding and prevention of the pathogenesis of amebiasis through the study of specific surface antigens. This will be accomplished using monoclonal antibodies to localize, characterize, and purify surface antigens. Monoclonal antibodies will be used to identify surface antigens by immunoblotting, radioimmunoprecipitation, agluttination, immunofluorescence and immunoprecipitation of surface antigens from live amoebae. Once identified, antigens will be purified by radioimmunoprecipitation alone or with radioimmunoprecipitation and electroelution followed by concentration. Biological properties relating to pathogenesis of purified antigens will be assessed by lymphocyte proliferation assays, macrophage activation assays, and monoclonal antibodies specific for these purified antigens to be assessed for ability to abrogate attachment of E. histolytica to target tissues thus preventing or slowing cytolysis of target tissue. In addition, identification of serologically relevant antigens will enable the purification of these moieties and testing of them to develop a defined antigen serological assay for the diagnosis of invasive amebiasis. The proposal relates directly to the identification and characterization of potential E. histolytica vaccinogens as invasive disease is preventable using crude antigen preparations. Identification of specific antigens which stimulate lymphocyte proliferation and/or macrophage activation is necessary to identify appropriate antigens for cloning and use in a potential vaccine. Similarly these specific antigens may be used to formulate a serological assay which is more sensitive and specific for invasive disease.